The invention relates to processes for the optical inspection of a transparent region of a container, in particular the mouth region of a bottle, in which an image of the region which can be observed by at least one camera is produced. The invention also relates to apparatus for carrying out the processes.
A process and an arrangement for optical inspection of a rotationally symmetrical body, in particular for inspecting bottle mouths with a screw thread, are known from the document EP-A-47936. Another apparatus for inspecting the mouth region of bottles which is intended to overcome drawbacks of the apparatus according to the first-mentioned document is known from the document EP-B-209077. However, a drawback of both forms of apparatus is that the bottle mouth region is illuminated by incident light, which makes inspection of the image produced at the camera difficult, as only relatively small differences in brightness result between clean undamaged bottles on the one hand and soiled and/or damaged bottles on the other hand. This is a particular problem in the case of bottles with screw threads which are provided with vertical slots (vent-slots). This applies eg. to returnable PET bottles.